Process for improving the properties of textile fibres



United States Patent 3,176,002 PROCESS FOR IMPROVING THE PROPERTIES OFTEXTILE FIBRES Luciano Nobile, Milan, Italy, assignor to Miled S.p.A.,Milan, Italy No Drawing. Filed Oct. 1, 1962, Ser. No. 227,543 Claimspriority, application Italy, Oct. 18, 1961, 18 ,814/ 61 2 Claims. (Cl.260-119) The present invention is concerned with a process for obtainingsynthetic and natural textile fibres having improved properties ofsoftness, tenacity and durability.

The process of the invention provides for the preparation of the fibresin a particularly simple and rapid manner. It consists essentially intreating the fibres, during the production process, with difierentamounts of dialdehyde starch which imparts to the fibres obtained at theend of the process, the above indicated desirable properties.

The usual preparation process of synthetic fibres consists of differentsteps, which can be summarized as follows.

(1) Solubilization of casein by the addition to its suspensions ofsodium hydroxide of varying concentration.

(2) Spinning of the dissolved casein (by immersion) in an acidic bathcontaining inorganic salts. This bath has generally the followingaverage composition:

Density at 20 C. 1.150-1.200 Acidity as H 80 g./l 70-80 Total salts g./l250-300 (3) Drawing of the thread in acidic saline solution usuallyhaving the following composition:

Density at 20 C. 1150-1200 Acidity as H 80 g./l 6-7 Aluminum sulfate,about g./l 50 Sodium chloride g./l 150-160 Various salts, about g./l 50(4) Cutting of the fibre and tanning with formaldehyde in a salinesolution of about the following composition:

Density at 20 C. 1.l50-l.200 Acidity as H 80 g./l -6 Total salts, aboutg./l 200 Formaldehyde g./l

(5) Washing and drying.

By the process described in the present application, spinning, drawingand tanning are carried out very rapidly in one single step and in asingle bath, thus providing a considerable gain in time over the knownprocedures. Moreover, tanning is not performed with formaldehyde. It isknown that the use of formaldehyde, due to its persistant odor, impliesan expensive working in closed containers and does not allow theproduction of continuous threads. The dialdehyde starch used in theprocess of the invention has no persistent odor or irritating action, sothat it is possible to work in open containers. Finally as the durationof tanning is limited to a very short contact period in comparison withthe known methods (no longer than 30 minutes) continuous threads areeasily obtained.

Due to the length of the chain of the dialdehyde starch molecule thereare obtained fibres having a ratio between dry tenacity and wet tenacityconsiderably improved in 3,176,002 Patented Mar. 30, 1965 comparisonwith the fibres obtained by analogous procedures. It is known that incommon proteic fibres the ratio is: dry tenacity 1 g. denier/wettenacity 0.4 g. denier. When tanning is carried out with dialdehydestarch, a dry tenacity of 1.2 g. denier and a wet tenacity of 0.6-0.7 g.denier is reached. This value of wet tenacity widely overcomes thelimits of security allowing the use of textile fibres.

For practical purposes the process of the invention is carried out asfollows. Casein is solubilized by the addition to its aqueous suspensionof a substance apt to neutralize free acid groups giving the solublesalts of casein, such as an alkali metal hydroxide, urea or any otherbasic organic substance with one or more free amino groups.

The casein solution so obtained is simultaneously spun stretched andpretanned in a bath having about the following composition:

G./l. Acid calculated as H about 50 Total salts, about 200-300Dialdehyde starch, about 20-50 Fixing auxiliary, about 2-10 Thispretanning is performed in acid solution and is followed by tanning inslightly alkaline bath containing from 100 to 200 g./l. of dialdehydestarch at a temperature between 30 and C.

At the end of this tanning the product is thoroughly Washed and dried.

Alternatively it is possible to carry out spinning, drawing and tanningin a single neutral bath containing 200- 250 g./l. of total salts and50-200 g./l. of dialdehyde starch. This last procedure represents aconsiderable improvement over the known processes and provides theobtainment of textile fibres of high quality in a shorter period oftime.

A detailed example which does not limit the invention is givenhereinafter; the scope of the invention being indicated by the subjoinedclaims.

Example Two hundred kilograms of casein are treated with 600 l. of waterand the mass is allowed to swell for 3.5 hours under stirring at roomtemperature. An amount of sodium hydroxide is added which is sufiicientto obtain a free alkalinity corresponding to 1 g./l. of NaOH. Water isadded to reach a total volume of 1000 1., the mixture is stirred for afurther 30 minutes, filtered through a press filter, air is removed invacuo and after 24 hours the mixture is transferred into a neutral bathcontaining g./l. of dialdehyde starch and 200 g./l. of total salts. Inthis bath spinning, drawing and tanning are carried out as abovedescribed. The fibre is then thoroughly washed and dried.

In comparison with a fibre obtained by an analogous process but withoutthe addition of dialdehyde starch to the bath, an improvement of the wetdynamometric characteristics of about 40% is obtained. Analogous resultsare obtained in the preparation of fibres derived from urea-caseinsolutions mixed with viscose-rayon or in the preparation of fibresderiving from solutions of ethylenediamine-casein.

We claim:

1. Process for preparing casein fibres which consists in submittingcasein, after solubilization of the same by the addition of a basicsubstance to its water suspension,

3 a to simultaneous spinning, drawing and tanning in an References Citedin the file of this patent aqueous bath containing 50400 g./l. ofdialdehyde t h UNITED STATES PATENTS s are 2. A casein fibre obtained bysubmitting casein after ggggigg gigs 5i a1 if 132% solubilization of thesame by the addition of a basic sub- 5 a 7" stance to its watersuspension to an alkaline reaction, to OTHER E ENCES simultaneousspinning, drawing and tanning in an aqueous Beebe et al.: Journal of theAmerican Leather Chembath containing 50-200 mg./l. of dialdehyde starch.

ists Assn, vol. LIV, N0. 11, pages 628-639 (1959).

1. PROCESS FOR PREPARING CASEIN FIBERS WHICH CONSISTS IN SUBMITTINGCASEIN, AFTER SOLUBILIZATION OF THE SAME BY THE ADDITION OF A BASICSUBSTANCE TO ITS WATER SUSPENSION, TO SIMULTANEOUS SPINNING, DRAWING ANDTANNING IN AN AQUEOUS BATH CONTAINING 50-200 G./1. OF DIALDEHYDE STARCH.